How do gun scopes work?
I understand iron sights because it aligns the back and front of the gun in the direction of the target, but how is the gun aligned with a scope? If you move your eye 3 mm to one side, does the crosshair stay on target? Does it have to do with the curve of the lens?
- Russ in NOVALv 71 month agoFavorite Answer
The phenomenon you speak of (effect of moving the eye off center) is called parallax and is a know property in scopes of any kind. There are many online articles about parallax that you can google, but briefly it is the optical relationship between the reticle in the scope and the focal plane of the projected target internal to the scope.
The curve of the objectives lens(es) in the front of the scope projects (the light from) a distant target to an imaginary plane inside the scope called the first focal plane. There are a second set of lenses inside the scope that project image on the first focal plane to the back of the scope onto second focal plane. The second set of lenses also flips the image upright (because the first focal plane is projects them upside down). There is a third set of ocular lenses that projects the image to the eye. The position of focal planes are slightly based on the distance to the target.
Scope manufacturers place the reticle to correspond to either the first focal plane or the second focal plane. A scope with a reticle at the first focal plane will appear to proportionally change size when the zoom is adjusted (on a variable magnification scope). A reticle placed at the second focal plane and will remain a constant size no matter what magnification is set to.If the reticle is placed exactly at the focal plane, there is no parallax and the reticle will not move relative to the target if the eye is moved off-center of the scope. However, as mentioned, the focal plane location changes slightly based on the distant target, so the second consideration for the manufacturer in positioning the reticle is to pick that position relative to a target range. Fixed parallax scopes are built to have the reticle placed so there is no parallax at a specific target range, usually 100 yards. Objects closer and further away will begin to exhibit parallax, but for most sport and hunting uses, this is not a big deal, especially if the user establishes a solid and consistent cheek weld, keeping the eye looking down the center of the scope.
For precision and long range shooters, scopes have an adjustable parallax (either by adjusting the objective or a knob on the side) to cover the full range of usage from as little as a few yards to infinity. Adjustable parallax models have controls that adjusts the optics slightly so that the focal plane can correspond to reticle position based on range, and also have the benefit of sharpening the image at the range selected.
- 1 month ago
scope good scope bad
- 1 month ago
Like I would give information to a ******* school shooter. Kill yourself mother ******.
- BBeanLv 71 month ago
A scope works kinda like your iron sights. You have an objective lens that has a convex lens that receives light and the image (according to the curve of the outer surface) projects a triangular image to the 1st focal plane reticle=front sight. Just like adjusting a front sight...the bullet goes east...move the sight blade west. The bullet goes up...move the sight blade down. Vise-Versa to both.
Then the triangular image from that point starts getting larger until received by the picture reversal assembly.(self explanatory) From that point the triangular image starts getting smaller until it gets to the aperture in the 2nd focal plane which=a rear peep sight. From there the triangular image starts getting large again until it gets to the ocular assembly which with a combination of concaves and convexes presents favorable images to your eye. Those images are adjustable by you for you and have little to nothing to do with the zeroing in on the target. Yep, the image is flipped a couple of times before it gets to what your eye/brain sees.
- How do you think about the answers? You can sign in to vote the answer.
- MattLv 61 month ago
Magnified optics are typically mounted to the top of the rifle slightly above the barrel. When optics are sighted in or "zeroed" this refers to the bullets trajectory and the point during its flight that it crosses the center of the reticle (cross-hairs). A person can change this when sighting in a scope. If someone sights it in for 100 yds that means the bullet will hit where the scope is aimed at 100 yards. If you move the target closer or further away without re-sighting your scope (scope remains sighted in at 100 yds) your point of aim (POA) and your point of impact (POI) will change.
If a person is not centered behing the optic when looking through it this can cause parallax shift. Some optics are designed to reduce this but it's essentially the apparent shift of an object's position relative to more distant background objects caused by a change in the observer's position.
- Burberry McChavLv 61 month ago
It's a telescope with a crosshair, you aim with the cross and yes the cross moves with you moving the gun, if you move 3mm so will the cross, you don't line up anything to anything like open sights.
- ocularnervosaLv 71 month ago
You can only see the crosshairs on the scope while looking straight down it's barrel.
- Anonymous1 month ago